The present invention relates to a magnetic recording medium for use in a magnetic recording apparatus, such as a magnetic disk drive or a magnetic drum device.
Generally, in a magnetic recording apparatus having a recording/reproduction head (to be referred to as a head hereinafter) and a magnetic recording medium as its components, a method of recording and reproduction is as follows. That is, at the start of an operation, the head is set in contact with the surface of the magnetic recording medium, and the magnetic recording medium is rotated at a predetermined speed. As a result, a space serving as an air layer is formed between the head and the surface of the magnetic recording medium. In this state, a recording or reproduction operation is performed (this method will be referred to as a contact-start-stop system, or CSS hereinafter). In this method, the rotation of the magnetic recording medium stops at the end of the operation, and at this time the head and the surface of the magnetic recording medium are set in the contact state with a friction as when the operation is started.
A frictional force produced between the head and the magnetic recording medium in this contact state with a friction abrades the head and the magnetic recording medium and eventually may form scratches on the head and the magnetic recording medium. In addition, in the contact state with a friction, a slight change in position of the head makes a load applied on the head unbalanced. This may produce scratches on the surface of the head and that of the magnetic recording medium. In this case, the head is any one of a laminated alloy substrate consisting of, e.g., an aluminum alloy, a titanium alloy, or stainless steel and coated with a metal, plastic, or ceramic; a plastic substrate coated with a metal or ceramic; or a ceramic substrate coated with a metal or plastic. Furthermore, the head and the magnetic recording medium stick to each other due to a long-time contact between them and it consequently becomes difficult to separate them from each other.
In order to prevent the destruction and sticking of the magnetic recording medium caused by the contact and sliding with the head, a lubricant, such as perfluoropolyether, is conventionally coated on the surface of the magnetic recording medium, as described in Japanese Patent Laid-Open No. 52-49805. In addition, Japanese Patent Laid-Open No. 64-9961, 63-77996, or 62-45562 discloses a lubricant containing alkylperfluoroalkaneamide, perfluoroalkylcarboxylic acid amine salt, or perfluorocarboxylic acid ester.
A lubricant such as perfluoropolyether, however, has a low load resistance and therefore cannot prevent production of scratches on the magnetic recording medium upon sliding with the head or upon repetition of CSS by a large number of times. In addition, there is another problem that a thick layer of the removed lubricant is locally formed between the contact sliding surfaces of the magnetic recording medium and the head, and this makes it impossible to separate the head and the magnetic recording medium from each other. The lubricant using alkylperfluoroalkaneamide, perfluoroalkylcarboxylic amine salt, or perfluorocarboxylic acid ester is poor in orientation of molecules and consequently does not have adhesive force enough to hold lubricant molecules on the surface of the magnetic recording medium. This lubricant also has a disadvantage that it is removed upon sliding with the head.